<html><head><meta name="color-scheme" content="light dark"></head><body><pre style="word-wrap: break-word; white-space: pre-wrap;">package Fatal;

# ABSTRACT: Replace functions with equivalents which succeed or die

use 5.008;  # 5.8.x needed for autodie
use Carp;
use strict;
use warnings;
use Tie::RefHash;   # To cache subroutine refs
use Config;
use Scalar::Util qw(set_prototype looks_like_number);

use autodie::Util qw(
  fill_protos
  install_subs
  make_core_trampoline
  on_end_of_compile_scope
);

use constant PERL510     =&gt; ( $] &gt;= 5.010 );

use constant LEXICAL_TAG =&gt; q{:lexical};
use constant VOID_TAG    =&gt; q{:void};
use constant INSIST_TAG  =&gt; q{!};

# Keys for %Cached_fatalised_sub  (used in 3rd level)
use constant CACHE_AUTODIE_LEAK_GUARD    =&gt; 0;
use constant CACHE_FATAL_WRAPPER         =&gt; 1;
use constant CACHE_FATAL_VOID            =&gt; 2;


use constant ERROR_NOARGS    =&gt; 'Cannot use lexical %s with no arguments';
use constant ERROR_VOID_LEX  =&gt; VOID_TAG.' cannot be used with lexical scope';
use constant ERROR_LEX_FIRST =&gt; LEXICAL_TAG.' must be used as first argument';
use constant ERROR_NO_LEX    =&gt; "no %s can only start with ".LEXICAL_TAG;
use constant ERROR_BADNAME   =&gt; "Bad subroutine name for %s: %s";
use constant ERROR_NOTSUB    =&gt; "%s is not a Perl subroutine";
use constant ERROR_NOT_BUILT =&gt; "%s is neither a builtin, nor a Perl subroutine";
use constant ERROR_NOHINTS   =&gt; "No user hints defined for %s";

use constant ERROR_CANT_OVERRIDE =&gt; "Cannot make the non-overridable builtin %s fatal";

use constant ERROR_NO_IPC_SYS_SIMPLE =&gt; "IPC::System::Simple required for Fatalised/autodying system()";

use constant ERROR_IPC_SYS_SIMPLE_OLD =&gt; "IPC::System::Simple version %f required for Fatalised/autodying system().  We only have version %f";

use constant ERROR_AUTODIE_CONFLICT =&gt; q{"no autodie '%s'" is not allowed while "use Fatal '%s'" is in effect};

use constant ERROR_FATAL_CONFLICT =&gt; q{"use Fatal '%s'" is not allowed while "no autodie '%s'" is in effect};

use constant ERROR_58_HINTS =&gt; q{Non-subroutine %s hints for %s are not supported under Perl 5.8.x};

# Older versions of IPC::System::Simple don't support all the
# features we need.

use constant MIN_IPC_SYS_SIMPLE_VER =&gt; 0.12;

our $VERSION = '2.34'; # VERSION: Generated by DZP::OurPkg::Version

our $Debug ||= 0;

# EWOULDBLOCK values for systems that don't supply their own.
# Even though this is defined with our, that's to help our
# test code.  Please don't rely upon this variable existing in
# the future.

our %_EWOULDBLOCK = (
    MSWin32 =&gt; 33,
);

$Carp::CarpInternal{'Fatal'} = 1;
$Carp::CarpInternal{'autodie'} = 1;
$Carp::CarpInternal{'autodie::exception'} = 1;

# the linux parisc port has separate EAGAIN and EWOULDBLOCK,
# and the kernel returns EAGAIN
my $try_EAGAIN = ($^O eq 'linux' and $Config{archname} =~ /hppa|parisc/) ? 1 : 0;

# We have some tags that can be passed in for use with import.
# These are all assumed to be CORE::

my %TAGS = (
    ':io'      =&gt; [qw(:dbm :file :filesys :ipc :socket
                       read seek sysread syswrite sysseek )],
    ':dbm'     =&gt; [qw(dbmopen dbmclose)],
    ':file'    =&gt; [qw(open close flock sysopen fcntl binmode
                     ioctl truncate)],
    ':filesys' =&gt; [qw(opendir closedir chdir link unlink rename mkdir
                      symlink rmdir readlink chmod chown utime)],
    ':ipc'     =&gt; [qw(:msg :semaphore :shm pipe kill)],
    ':msg'     =&gt; [qw(msgctl msgget msgrcv msgsnd)],
    ':threads' =&gt; [qw(fork)],
    ':semaphore'=&gt;[qw(semctl semget semop)],
    ':shm'     =&gt; [qw(shmctl shmget shmread)],
    ':system'  =&gt; [qw(system exec)],

    # Can we use qw(getpeername getsockname)? What do they do on failure?
    # TODO - Can socket return false?
    ':socket'  =&gt; [qw(accept bind connect getsockopt listen recv send
                   setsockopt shutdown socketpair)],

    # Our defaults don't include system(), because it depends upon
    # an optional module, and it breaks the exotic form.
    #
    # This *may* change in the future.  I'd love IPC::System::Simple
    # to be a dependency rather than a recommendation, and hence for
    # system() to be autodying by default.

    ':default' =&gt; [qw(:io :threads)],

    # Everything in v2.07 and before. This was :default less chmod and chown
    ':v207'    =&gt; [qw(:threads :dbm :socket read seek sysread
                   syswrite sysseek open close flock sysopen fcntl fileno
                   binmode ioctl truncate opendir closedir chdir link unlink
                   rename mkdir symlink rmdir readlink umask
                   :msg :semaphore :shm pipe)],

    # Chmod was added in 2.13
    ':v213'    =&gt; [qw(:v207 chmod)],

    # chown, utime, kill were added in 2.14
    ':v214'    =&gt; [qw(:v213 chown utime kill)],

    # umask was removed in 2.26
    ':v225' =&gt; [qw(:io :threads umask fileno)],

    # Version specific tags.  These allow someone to specify
    # use autodie qw(:1.994) and know exactly what they'll get.

    ':1.994' =&gt; [qw(:v207)],
    ':1.995' =&gt; [qw(:v207)],
    ':1.996' =&gt; [qw(:v207)],
    ':1.997' =&gt; [qw(:v207)],
    ':1.998' =&gt; [qw(:v207)],
    ':1.999' =&gt; [qw(:v207)],
    ':1.999_01' =&gt; [qw(:v207)],
    ':2.00'  =&gt; [qw(:v207)],
    ':2.01'  =&gt; [qw(:v207)],
    ':2.02'  =&gt; [qw(:v207)],
    ':2.03'  =&gt; [qw(:v207)],
    ':2.04'  =&gt; [qw(:v207)],
    ':2.05'  =&gt; [qw(:v207)],
    ':2.06'  =&gt; [qw(:v207)],
    ':2.06_01' =&gt; [qw(:v207)],
    ':2.07'  =&gt; [qw(:v207)],     # Last release without chmod
    ':2.08'  =&gt; [qw(:v213)],
    ':2.09'  =&gt; [qw(:v213)],
    ':2.10'  =&gt; [qw(:v213)],
    ':2.11'  =&gt; [qw(:v213)],
    ':2.12'  =&gt; [qw(:v213)],
    ':2.13'  =&gt; [qw(:v213)],     # Last release without chown
    ':2.14'  =&gt; [qw(:v225)],
    ':2.15'  =&gt; [qw(:v225)],
    ':2.16'  =&gt; [qw(:v225)],
    ':2.17'  =&gt; [qw(:v225)],
    ':2.18'  =&gt; [qw(:v225)],
    ':2.19'  =&gt; [qw(:v225)],
    ':2.20'  =&gt; [qw(:v225)],
    ':2.21'  =&gt; [qw(:v225)],
    ':2.22'  =&gt; [qw(:v225)],
    ':2.23'  =&gt; [qw(:v225)],
    ':2.24'  =&gt; [qw(:v225)],
    ':2.25'  =&gt; [qw(:v225)],
    ':2.26'  =&gt; [qw(:default)],
    ':2.27'  =&gt; [qw(:default)],
    ':2.28'  =&gt; [qw(:default)],
    ':2.29'  =&gt; [qw(:default)],
    ':2.30'  =&gt; [qw(:default)],
    ':2.31'  =&gt; [qw(:default)],
    ':2.32'  =&gt; [qw(:default)],
    ':2.33'  =&gt; [qw(:default)],
    ':2.34'  =&gt; [qw(:default)],
);


{
    # Expand :all immediately by expanding and flattening all tags.
    # _expand_tag is not really optimised for expanding the ":all"
    # case (i.e. keys %TAGS, or values %TAGS for that matter), so we
    # just do it here.
    #
    # NB: The %tag_cache/_expand_tag relies on $TAGS{':all'} being
    # pre-expanded.
    my %seen;
    my @all = grep {
        !/^:/ &amp;&amp; !$seen{$_}++
    } map { @{$_} } values %TAGS;
    $TAGS{':all'} = \@all;
}

# This hash contains subroutines for which we should
# subroutine() // die() rather than subroutine() || die()

my %Use_defined_or;

# CORE::open returns undef on failure.  It can legitimately return
# 0 on success, eg: open(my $fh, '-|') || exec(...);

@Use_defined_or{qw(
    CORE::fork
    CORE::recv
    CORE::send
    CORE::open
    CORE::fileno
    CORE::read
    CORE::readlink
    CORE::sysread
    CORE::syswrite
    CORE::sysseek
    CORE::umask
)} = ();

# Some functions can return true because they changed *some* things, but
# not all of them.  This is a list of offending functions, and how many
# items to subtract from @_ to determine the "success" value they return.

my %Returns_num_things_changed = (
    'CORE::chmod'  =&gt; 1,
    'CORE::chown'  =&gt; 2,
    'CORE::kill'   =&gt; 1,  # TODO: Could this return anything on negative args?
    'CORE::unlink' =&gt; 0,
    'CORE::utime'  =&gt; 2,
);

# Optional actions to take on the return value before returning it.

my %Retval_action = (
    "CORE::open"        =&gt; q{

    # apply the open pragma from our caller
    if( defined $retval &amp;&amp; !( @_ &gt;= 3 &amp;&amp; $_[1] =~ /:/ )) {
        # Get the caller's hint hash
        my $hints = (caller 0)[10];

        # Decide if we're reading or writing and apply the appropriate encoding
        # These keys are undocumented.
        # Match what PerlIO_context_layers() does.  Read gets the read layer,
        # everything else gets the write layer.
        my $encoding = $_[1] =~ /^\+?&gt;/ ? $hints-&gt;{"open&gt;"} : $hints-&gt;{"open&lt;"};

        # Apply the encoding, if any.
        if( $encoding ) {
            binmode $_[0], $encoding;
        }
    }

},
    "CORE::sysopen"     =&gt; q{

    # apply the open pragma from our caller
    if( defined $retval ) {
        # Get the caller's hint hash
        my $hints = (caller 0)[10];

        require Fcntl;

        # Decide if we're reading or writing and apply the appropriate encoding.
        # Match what PerlIO_context_layers() does.  Read gets the read layer,
        # everything else gets the write layer.
        my $open_read_only = !($_[2] ^ Fcntl::O_RDONLY());
        my $encoding = $open_read_only ? $hints-&gt;{"open&lt;"} : $hints-&gt;{"open&gt;"};

        # Apply the encoding, if any.
        if( $encoding ) {
            binmode $_[0], $encoding;
        }
    }

},
);

my %reusable_builtins;

# "Wait!" I hear you cry, "truncate() and chdir() are not reuseable! They can
# take file and directory handles, which are package depedent."
#
# You would be correct, except that prototype() returns signatures which don't
# allow for passing of globs, and nobody's complained about that. You can
# still use \*FILEHANDLE, but that results in a reference coming through,
# and it's already pointing to the filehandle in the caller's packge, so
# it's all okay.

@reusable_builtins{qw(
    CORE::fork
    CORE::kill
    CORE::truncate
    CORE::chdir
    CORE::link
    CORE::unlink
    CORE::rename
    CORE::mkdir
    CORE::symlink
    CORE::rmdir
    CORE::readlink
    CORE::umask
    CORE::chmod
    CORE::chown
    CORE::utime
    CORE::msgctl
    CORE::msgget
    CORE::msgrcv
    CORE::msgsnd
    CORE::semctl
    CORE::semget
    CORE::semop
    CORE::shmctl
    CORE::shmget
    CORE::shmread
    CORE::exec
    CORE::system
)} = ();

# Cached_fatalised_sub caches the various versions of our
# fatalised subs as they're produced.  This means we don't
# have to build our own replacement of CORE::open and friends
# for every single package that wants to use them.

my %Cached_fatalised_sub = ();

# Every time we're called with package scope, we record the subroutine
# (including package or CORE::) in %Package_Fatal.  This allows us
# to detect illegal combinations of autodie and Fatal, and makes sure
# we don't accidently make a Fatal function autodying (which isn't
# very useful).

my %Package_Fatal = ();

# The first time we're called with a user-sub, we cache it here.
# In the case of a "no autodie ..." we put back the cached copy.

my %Original_user_sub = ();

# Is_fatalised_sub simply records a big map of fatalised subroutine
# refs.  It means we can avoid repeating work, or fatalising something
# we've already processed.

my  %Is_fatalised_sub = ();
tie %Is_fatalised_sub, 'Tie::RefHash';

# Our trampoline cache allows us to cache trampolines which are used to
# bounce leaked wrapped core subroutines to their actual core counterparts.

my %Trampoline_cache;

# A cache mapping "CORE::&lt;name&gt;" to their prototype.  Turns out that if
# you "use autodie;" enough times, this pays off.
my %CORE_prototype_cache;

# We use our package in a few hash-keys.  Having it in a scalar is
# convenient.  The "guard $PACKAGE" string is used as a key when
# setting up lexical guards.

my $PACKAGE       = __PACKAGE__;
my $NO_PACKAGE    = "no $PACKAGE";      # Used to detect 'no autodie'

# Here's where all the magic happens when someone write 'use Fatal'
# or 'use autodie'.

sub import {
    my $class        = shift(@_);
    my @original_args = @_;
    my $void         = 0;
    my $lexical      = 0;
    my $insist_hints = 0;

    my ($pkg, $filename) = caller();

    @_ or return;   # 'use Fatal' is a no-op.

    # If we see the :lexical flag, then _all_ arguments are
    # changed lexically

    if ($_[0] eq LEXICAL_TAG) {
        $lexical = 1;
        shift @_;

        # It is currently an implementation detail that autodie is
        # implemented as "use Fatal qw(:lexical ...)".  For backwards
        # compatibility, we allow it - but not without a warning.
        # NB: Optimise for autodie as it is quite possibly the most
        # freq. consumer of this case.
        if ($class ne 'autodie' and not $class-&gt;isa('autodie')) {
            if ($class eq 'Fatal') {
                warnings::warnif(
                    'deprecated',
                    '[deprecated] The "use Fatal qw(:lexical ...)" '
                    . 'should be replaced by "use autodie qw(...)". '
                    . 'Seen' # warnif appends " at &lt;...&gt;"
                    );
            } else {
                warnings::warnif(
                    'deprecated',
                    "[deprecated] The class/Package $class is a "
                    . 'subclass of Fatal and used the :lexical. '
                    . 'If $class provides lexical error checking '
                    . 'it should extend autodie instead of using :lexical. '
                    . 'Seen' # warnif appends " at &lt;...&gt;"
                    );
            }
            # "Promote" the call to autodie from here on.  This is
            # already mostly the case (e.g. use Fatal qw(:lexical ...)
            # would throw autodie::exceptions on error rather than the
            # Fatal errors.
            $class = 'autodie';
            # This requires that autodie is in fact loaded; otherwise
            # the "$class-&gt;X()" method calls below will explode.
            require autodie;
            # TODO, when autodie and Fatal are cleanly separated, we
            # should go a "goto &amp;autodie::import" here instead.
        }

        # If we see no arguments and :lexical, we assume they
        # wanted ':default'.

        if (@_ == 0) {
            push(@_, ':default');
        }

        # Don't allow :lexical with :void, it's needlessly confusing.
        if ( grep { $_ eq VOID_TAG } @_ ) {
            croak(ERROR_VOID_LEX);
        }
    }

    if ( grep { $_ eq LEXICAL_TAG } @_ ) {
        # If we see the lexical tag as the non-first argument, complain.
        croak(ERROR_LEX_FIRST);
    }

    my @fatalise_these =  @_;

    # These subs will get unloaded at the end of lexical scope.
    my %unload_later;
    # These subs are to be installed into callers namespace.
    my %install_subs;

    # Use _translate_import_args to expand tags for us.  It will
    # pass-through unknown tags (i.e. we have to manually handle
    # VOID_TAG).
    #
    # NB: _translate_import_args re-orders everything for us, so
    # we don't have to worry about stuff like:
    #
    #     :default :void :io
    #
    # That will (correctly) translated into
    #
    #     expand(:defaults-without-io) :void :io
    #
    # by _translate_import_args.
    for my $func ($class-&gt;_translate_import_args(@fatalise_these)) {

        if ($func eq VOID_TAG) {

            # When we see :void, set the void flag.
            $void = 1;

        } elsif ($func eq INSIST_TAG) {

            $insist_hints = 1;

        } else {

            # Otherwise, fatalise it.

            # Check to see if there's an insist flag at the front.
            # If so, remove it, and insist we have hints for this sub.
            my $insist_this = $insist_hints;

            if (substr($func, 0, 1) eq '!') {
                $func = substr($func, 1);
                $insist_this = 1;
            }

            # We're going to make a subroutine fatalistic.
            # However if we're being invoked with 'use Fatal qw(x)'
            # and we've already been called with 'no autodie qw(x)'
            # in the same scope, we consider this to be an error.
            # Mixing Fatal and autodie effects was considered to be
            # needlessly confusing on p5p.

            my $sub = $func;
            $sub = "${pkg}::$sub" unless $sub =~ /::/;

            # If we're being called as Fatal, and we've previously
            # had a 'no X' in scope for the subroutine, then complain
            # bitterly.

            if (! $lexical and $^H{$NO_PACKAGE}{$sub}) {
                 croak(sprintf(ERROR_FATAL_CONFLICT, $func, $func));
            }

            # We're not being used in a confusing way, so make
            # the sub fatal.  Note that _make_fatal returns the
            # old (original) version of the sub, or undef for
            # built-ins.

            my $sub_ref = $class-&gt;_make_fatal(
                $func, $pkg, $void, $lexical, $filename,
                $insist_this, \%install_subs,
            );

            $Original_user_sub{$sub} ||= $sub_ref;

            # If we're making lexical changes, we need to arrange
            # for them to be cleaned at the end of our scope, so
            # record them here.

            $unload_later{$func} = $sub_ref if $lexical;
        }
    }

    install_subs($pkg, \%install_subs);

    if ($lexical) {

        # Dark magic to have autodie work under 5.8
        # Copied from namespace::clean, that copied it from
        # autobox, that found it on an ancient scroll written
        # in blood.

        # This magic bit causes %^H to be lexically scoped.

        $^H |= 0x020000;

        # Our package guard gets invoked when we leave our lexical
        # scope.

        on_end_of_compile_scope(sub {
            install_subs($pkg, \%unload_later);
        });

        # To allow others to determine when autodie was in scope,
        # and with what arguments, we also set a %^H hint which
        # is how we were called.

        # This feature should be considered EXPERIMENTAL, and
        # may change without notice.  Please e-mail pjf@cpan.org
        # if you're actually using it.

        $^H{autodie} = "$PACKAGE @original_args";

    }

    return;

}

sub unimport {
    my $class = shift;

    # Calling "no Fatal" must start with ":lexical"
    if ($_[0] ne LEXICAL_TAG) {
        croak(sprintf(ERROR_NO_LEX,$class));
    }

    shift @_;   # Remove :lexical

    my $pkg = (caller)[0];

    # If we've been called with arguments, then the developer
    # has explicitly stated 'no autodie qw(blah)',
    # in which case, we disable Fatalistic behaviour for 'blah'.

    my @unimport_these = @_ ? @_ : ':all';
    my (%uninstall_subs, %reinstall_subs);

    for my $symbol ($class-&gt;_translate_import_args(@unimport_these)) {

        my $sub = $symbol;
        $sub = "${pkg}::$sub" unless $sub =~ /::/;

        # If 'blah' was already enabled with Fatal (which has package
        # scope) then, this is considered an error.

        if (exists $Package_Fatal{$sub}) {
            croak(sprintf(ERROR_AUTODIE_CONFLICT,$symbol,$symbol));
        }

        # Record 'no autodie qw($sub)' as being in effect.
        # This is to catch conflicting semantics elsewhere
        # (eg, mixing Fatal with no autodie)

        $^H{$NO_PACKAGE}{$sub} = 1;
        # Record the current sub to be reinstalled at end of scope
        # and then restore the original (can be undef for "CORE::"
        # subs)

        {
            no strict 'refs';  ## no critic # to avoid: Can't use string (...) as a symbol ref ...
            $reinstall_subs{$symbol} = \&amp;$sub
                if exists ${"${pkg}::"}{$symbol};
        }
        $uninstall_subs{$symbol} = $Original_user_sub{$sub};

    }

    install_subs($pkg, \%uninstall_subs);
    on_end_of_compile_scope(sub {
        install_subs($pkg, \%reinstall_subs);
    });

    return;

}

sub _translate_import_args {
    my ($class, @args) = @_;
    my @result;
    my %seen;

    if (@args &lt; 2) {
        # Optimize for this case, as it is fairly common.  (e.g. use
        # autodie; or use autodie qw(:all); both trigger this).
        return unless @args;

        # Not a (known) tag, pass through.
        return @args unless exists($TAGS{$args[0]});

        # Strip "CORE::" from all elements in the list as import and
        # unimport does not handle the "CORE::" prefix too well.
        #
        # NB: we use substr as it is faster than s/^CORE::// and
        # it does not change the elements.
        return map { substr($_, 6) } @{ $class-&gt;_expand_tag($args[0]) };
    }

    # We want to translate
    #
    #     :default :void :io
    #
    # into (pseudo-ish):
    #
    #     expanded(:threads) :void expanded(:io)
    #
    # We accomplish this by "reverse, expand + filter, reverse".
    for my $a (reverse(@args)) {
        if (exists $TAGS{$a}) {
            my $expanded = $class-&gt;_expand_tag($a);
            push(@result,
                 # Remove duplicates after ...
                 grep { !$seen{$_}++ }
                 # we have stripped CORE:: (see above)
                 map { substr($_, 6) }
                 # We take the elements in reverse order
                 # (as @result be reversed later).
                 reverse(@{$expanded}));
        } else {
            # pass through - no filtering here for tags.
            #
            # The reason for not filtering tags cases like:
            #
            #    ":default :void :io :void :threads"
            #
            # As we have reversed args, we see this as:
            #
            #    ":threads :void :io :void* :default*"
            #
            # (Entries marked with "*" will be filtered out completely).  When
            # reversed again, this will be:
            #
            #    ":io :void :threads"
            #
            # But we would rather want it to be:
            #
            #    ":void :io :threads" or ":void :io :void :threads"
            #

            my $letter = substr($a, 0, 1);
            if ($letter ne ':' &amp;&amp; $a ne INSIST_TAG) {
                next if $seen{$a}++;
                if ($letter eq '!' and $seen{substr($a, 1)}++) {
                    my $name = substr($a, 1);
                    # People are being silly and doing:
                    #
                    #    use autodie qw(!a a);
                    #
                    # Enjoy this little O(n) clean up...
                    @result = grep { $_ ne $name } @result;
                }
            }
            push @result, $a;
        }
    }
    # Reverse the result to restore the input order
    return reverse(@result);
}


# NB: Perl::Critic's dump-autodie-tag-contents depends upon this
# continuing to work.

{
    # We assume that $TAGS{':all'} is pre-expanded and just fill it in
    # from the beginning.
    my %tag_cache = (
        'all' =&gt; [map { "CORE::$_" } @{$TAGS{':all'}}],
    );

    # Expand a given tag (e.g. ":default") into a listref containing
    # all sub names covered by that tag.  Each sub is returned as
    # "CORE::&lt;name&gt;" (i.e. "CORE::open" rather than "open").
    #
    # NB: the listref must not be modified.
    sub _expand_tag {
        my ($class, $tag) = @_;

        if (my $cached = $tag_cache{$tag}) {
            return $cached;
        }

        if (not exists $TAGS{$tag}) {
            croak "Invalid exception class $tag";
        }

        my @to_process = @{$TAGS{$tag}};

        # If the tag is basically an alias of another tag (like e.g. ":2.11"),
        # then just share the resulting reference with the original content (so
        # we only pay for an extra reference for the alias memory-wise).
        if (@to_process == 1 &amp;&amp; substr($to_process[0], 0, 1) eq ':') {
            # We could do this for "non-tags" as well, but that only occurs
            # once at the time of writing (":threads" =&gt; ["fork"]), so
            # probably not worth it.
            my $expanded = $class-&gt;_expand_tag($to_process[0]);
            $tag_cache{$tag} = $expanded;
            return $expanded;
        }

        my %seen = ();
        my @taglist = ();

        for my $item (@to_process) {
            # substr is more efficient than m/^:/ for stuff like this,
            # at the price of being a bit more verbose/low-level.
            if (substr($item, 0, 1) eq ':') {
                # Use recursion here to ensure we expand a tag at most once.

                my $expanded = $class-&gt;_expand_tag($item);
                push @taglist, grep { !$seen{$_}++ } @{$expanded};
            } else {
                my $subname = "CORE::$item";
                push @taglist, $subname
                    unless $seen{$subname}++;
            }
        }

        $tag_cache{$tag} = \@taglist;

        return \@taglist;

    }

}

# This is a backwards compatible version of _write_invocation.  It's
# recommended you don't use it.

sub write_invocation {
    my ($core, $call, $name, $void, @args) = @_;

    return Fatal-&gt;_write_invocation(
        $core, $call, $name, $void,
        0,      # Lexical flag
        undef,  # Sub, unused in legacy mode
        undef,  # Subref, unused in legacy mode.
        @args
    );
}

# This version of _write_invocation is used internally.  It's not
# recommended you call it from external code, as the interface WILL
# change in the future.

sub _write_invocation {

    my ($class, $core, $call, $name, $void, $lexical, $sub, $sref, @argvs) = @_;

    if (@argvs == 1) {        # No optional arguments

        my @argv = @{$argvs[0]};
        shift @argv;

        return $class-&gt;_one_invocation($core,$call,$name,$void,$sub,! $lexical, $sref, @argv);

    } else {
        my $else = "\t";
        my (@out, @argv, $n);
        while (@argvs) {
            @argv = @{shift @argvs};
            $n = shift @argv;

            my $condition = "\@_ == $n";

            if (@argv and $argv[-1] =~ /[#@]_/) {
                # This argv ends with '@' in the prototype, so it matches
                # any number of args &gt;= the number of expressions in the
                # argv.
                $condition = "\@_ &gt;= $n";
            }

            push @out, "${else}if ($condition) {\n";

            $else = "\t} els";

        push @out, $class-&gt;_one_invocation($core,$call,$name,$void,$sub,! $lexical, $sref, @argv);
        }
        push @out, qq[
            }
            die "Internal error: $name(\@_): Do not expect to get ", scalar(\@_), " arguments";
    ];

        return join '', @out;
    }
}


# This is a slim interface to ensure backward compatibility with
# anyone doing very foolish things with old versions of Fatal.

sub one_invocation {
    my ($core, $call, $name, $void, @argv) = @_;

    return Fatal-&gt;_one_invocation(
        $core, $call, $name, $void,
        undef,   # Sub.  Unused in back-compat mode.
        1,       # Back-compat flag
        undef,   # Subref, unused in back-compat mode.
        @argv
    );

}

# This is the internal interface that generates code.
# NOTE: This interface WILL change in the future.  Please do not
# call this subroutine directly.

# TODO: Whatever's calling this code has already looked up hints.  Pass
# them in, rather than look them up a second time.

sub _one_invocation {
    my ($class, $core, $call, $name, $void, $sub, $back_compat, $sref, @argv) = @_;


    # If someone is calling us directly (a child class perhaps?) then
    # they could try to mix void without enabling backwards
    # compatibility.  We just don't support this at all, so we gripe
    # about it rather than doing something unwise.

    if ($void and not $back_compat) {
        Carp::confess("Internal error: :void mode not supported with $class");
    }

    # @argv only contains the results of the in-built prototype
    # function, and is therefore safe to interpolate in the
    # code generators below.

    # TODO - The following clobbers context, but that's what the
    #        old Fatal did.  Do we care?

    if ($back_compat) {

        # Use Fatal qw(system) will never be supported.  It generated
        # a compile-time error with legacy Fatal, and there's no reason
        # to support it when autodie does a better job.

        if ($call eq 'CORE::system') {
            return q{
                croak("UNIMPLEMENTED: use Fatal qw(system) not supported.");
            };
        }

        local $" = ', ';

        if ($void) {
            return qq/return (defined wantarray)?$call(@argv):
                   $call(@argv) || Carp::croak("Can't $name(\@_)/ .
                   ($core ? ': $!' : ', \$! is \"$!\"') . '")'
        } else {
            return qq{return $call(@argv) || Carp::croak("Can't $name(\@_)} .
                   ($core ? ': $!' : ', \$! is \"$!\"') . '")';
        }
    }

    # The name of our original function is:
    #   $call if the function is CORE
    #   $sub if our function is non-CORE

    # The reason for this is that $call is what we're actually
    # calling.  For our core functions, this is always
    # CORE::something.  However for user-defined subs, we're about to
    # replace whatever it is that we're calling; as such, we actually
    # calling a subroutine ref.

    my $human_sub_name = $core ? $call : $sub;

    # Should we be testing to see if our result is defined, or
    # just true?

    my $use_defined_or;

    my $hints;      # All user-sub hints, including list hints.

    if ( $core ) {

        # Core hints are built into autodie.

        $use_defined_or = exists ( $Use_defined_or{$call} );

    }
    else {

        # User sub hints are looked up using autodie::hints,
        # since users may wish to add their own hints.

        require autodie::hints;

        $hints = autodie::hints-&gt;get_hints_for( $sref );

        # We'll look up the sub's fullname.  This means we
        # get better reports of where it came from in our
        # error messages, rather than what imported it.

        $human_sub_name = autodie::hints-&gt;sub_fullname( $sref );

    }

    # Checks for special core subs.

    if ($call eq 'CORE::system') {

        # Leverage IPC::System::Simple if we're making an autodying
        # system.

        local $" = ", ";

        # We need to stash $@ into $E, rather than using
        # local $@ for the whole sub.  If we don't then
        # any exceptions from internal errors in autodie/Fatal
        # will mysteriously disappear before propagating
        # upwards.

        return qq{
            my \$retval;
            my \$E;


            {
                local \$@;

                eval {
                    \$retval = IPC::System::Simple::system(@argv);
                };

                \$E = \$@;
            }

            if (\$E) {

                # TODO - This can't be overridden in child
                # classes!

                die autodie::exception::system-&gt;new(
                    function =&gt; q{CORE::system}, args =&gt; [ @argv ],
                    message =&gt; "\$E", errno =&gt; \$!,
                );
            }

            return \$retval;
        };

    }

    local $" = ', ';

    # If we're going to throw an exception, here's the code to use.
    my $die = qq{
        die $class-&gt;throw(
            function =&gt; q{$human_sub_name}, args =&gt; [ @argv ],
            pragma =&gt; q{$class}, errno =&gt; \$!,
            context =&gt; \$context, return =&gt; \$retval,
            eval_error =&gt; \$@
        )
    };

    if ($call eq 'CORE::flock') {

        # flock needs special treatment.  When it fails with
        # LOCK_UN and EWOULDBLOCK, then it's not really fatal, it just
        # means we couldn't get the lock right now.

        require POSIX;      # For POSIX::EWOULDBLOCK

        local $@;   # Don't blat anyone else's $@.

        # Ensure that our vendor supports EWOULDBLOCK.  If they
        # don't (eg, Windows), then we use known values for its
        # equivalent on other systems.

        my $EWOULDBLOCK = eval { POSIX::EWOULDBLOCK(); }
                          || $_EWOULDBLOCK{$^O}
                          || _autocroak("Internal error - can't overload flock - EWOULDBLOCK not defined on this system.");
        my $EAGAIN = $EWOULDBLOCK;
        if ($try_EAGAIN) {
            $EAGAIN = eval { POSIX::EAGAIN(); }
                          || _autocroak("Internal error - can't overload flock - EAGAIN not defined on this system.");
        }

        require Fcntl;      # For Fcntl::LOCK_NB

        return qq{

            my \$context = wantarray() ? "list" : "scalar";

            # Try to flock.  If successful, return it immediately.

            my \$retval = $call(@argv);
            return \$retval if \$retval;

            # If we failed, but we're using LOCK_NB and
            # returned EWOULDBLOCK, it's not a real error.

            if (\$_[1] &amp; Fcntl::LOCK_NB() and
                (\$! == $EWOULDBLOCK or
                ($try_EAGAIN and \$! == $EAGAIN ))) {
                return \$retval;
            }

            # Otherwise, we failed.  Die noisily.

            $die;

        };
    }

    if ($call eq 'CORE::kill') {

        return qq[

            my \$num_things = \@_ - $Returns_num_things_changed{$call};
            my \$context = ! defined wantarray() ? 'void' : 'scalar';
            my \$signal = \$_[0];
            my \$retval = $call(@argv);
            my \$sigzero = looks_like_number( \$signal ) &amp;&amp; \$signal == 0;

            if (    (   \$sigzero &amp;&amp; \$context eq 'void' )
                 or ( ! \$sigzero &amp;&amp; \$retval != \$num_things ) ) {

                $die;
            }

            return \$retval;
        ];
    }

    if (exists $Returns_num_things_changed{$call}) {

        # Some things return the number of things changed (like
        # chown, kill, chmod, etc). We only consider these successful
        # if *all* the things are changed.

        return qq[
            my \$num_things = \@_ - $Returns_num_things_changed{$call};
            my \$retval = $call(@argv);

            if (\$retval != \$num_things) {

                # We need \$context to throw an exception.
                # It's *always* set to scalar, because that's how
                # autodie calls chown() above.

                my \$context = "scalar";
                $die;
            }

            return \$retval;
        ];
    }

    # AFAIK everything that can be given an unopned filehandle
    # will fail if it tries to use it, so we don't really need
    # the 'unopened' warning class here.  Especially since they
    # then report the wrong line number.

    # Other warnings are disabled because they produce excessive
    # complaints from smart-match hints under 5.10.1.

    my $code = qq[
        no warnings qw(unopened uninitialized numeric);
        no if \$\] &gt;= 5.017011, warnings =&gt; "experimental::smartmatch";

        if (wantarray) {
            my \@results = $call(@argv);
            my \$retval  = \\\@results;
            my \$context = "list";

    ];

    my $retval_action = $Retval_action{$call} || '';

    if ( $hints and ( ref($hints-&gt;{list} ) || "" ) eq 'CODE' ) {

        # NB: Subroutine hints are passed as a full list.
        # This differs from the 5.10.0 smart-match behaviour,
        # but means that context unaware subroutines can use
        # the same hints in both list and scalar context.

        $code .= qq{
            if ( \$hints-&gt;{list}-&gt;(\@results) ) { $die };
        };
    }
    elsif ( PERL510 and $hints ) {
        $code .= qq{
            if ( \@results ~~ \$hints-&gt;{list} ) { $die };
        };
    }
    elsif ( $hints ) {
        croak sprintf(ERROR_58_HINTS, 'list', $sub);
    }
    else {
        $code .= qq{
            # An empty list, or a single undef is failure
            if (! \@results or (\@results == 1 and ! defined \$results[0])) {
                $die;
            }
        }
    }

    # Tidy up the end of our wantarray call.

    $code .= qq[
            return \@results;
        }
    ];


    # Otherwise, we're in scalar context.
    # We're never in a void context, since we have to look
    # at the result.

    $code .= qq{
        my \$retval  = $call(@argv);
        my \$context = "scalar";
    };

    if ( $hints and ( ref($hints-&gt;{scalar} ) || "" ) eq 'CODE' ) {

        # We always call code refs directly, since that always
        # works in 5.8.x, and always works in 5.10.1

        return $code .= qq{
            if ( \$hints-&gt;{scalar}-&gt;(\$retval) ) { $die };
            $retval_action
            return \$retval;
        };

    }
    elsif (PERL510 and $hints) {
        return $code . qq{

            if ( \$retval ~~ \$hints-&gt;{scalar} ) { $die };
            $retval_action
            return \$retval;
        };
    }
    elsif ( $hints ) {
        croak sprintf(ERROR_58_HINTS, 'scalar', $sub);
    }

    return $code .
    ( $use_defined_or ? qq{

        $die if not defined \$retval;
        $retval_action
        return \$retval;

    } : qq{

        $retval_action
        return \$retval || $die;

    } ) ;

}

# This returns the old copy of the sub, so we can
# put it back at end of scope.

# TODO : Check to make sure prototypes are restored correctly.

# TODO: Taking a huge list of arguments is awful.  Rewriting to
#       take a hash would be lovely.

# TODO - BACKCOMPAT - This is not yet compatible with 5.10.0

sub _make_fatal {
    my($class, $sub, $pkg, $void, $lexical, $filename, $insist, $install_subs) = @_;
    my($code, $sref, $proto, $core, $call, $hints, $cache, $cache_type);
    my $ini = $sub;
    my $name = $sub;


    if (index($sub, '::') == -1) {
        $sub = "${pkg}::$sub";
        if (substr($name, 0, 1) eq '&amp;') {
            $name = substr($name, 1);
        }
    } else {
        $name =~ s/.*:://;
    }


    # Figure if we're using lexical or package semantics and
    # twiddle the appropriate bits.

    if (not $lexical) {
        $Package_Fatal{$sub} = 1;
    }

    # TODO - We *should* be able to do skipping, since we know when
    # we've lexicalised / unlexicalised a subroutine.


    warn  "# _make_fatal: sub=$sub pkg=$pkg name=$name void=$void\n" if $Debug;
    croak(sprintf(ERROR_BADNAME, $class, $name)) unless $name =~ /^\w+$/;

    if (defined(&amp;$sub)) {   # user subroutine

        # NOTE: Previously we would localise $@ at this point, so
        # the following calls to eval {} wouldn't interfere with anything
        # that's already in $@.  Unfortunately, it would also stop
        # any of our croaks from triggering(!), which is even worse.

        # This could be something that we've fatalised that
        # was in core.

	# Store the current sub in case we need to restore it.
	$sref = \&amp;$sub;

        if ( $Package_Fatal{$sub} and exists($CORE_prototype_cache{"CORE::$name"})) {

            # Something we previously made Fatal that was core.
            # This is safe to replace with an autodying to core
            # version.

            $core  = 1;
            $call  = "CORE::$name";
            $proto = $CORE_prototype_cache{$call};

            # We return our $sref from this subroutine later
            # on, indicating this subroutine should be placed
            # back when we're finished.



        } else {

            # If this is something we've already fatalised or played with,
            # then look-up the name of the original sub for the rest of
            # our processing.

            if (exists($Is_fatalised_sub{$sref})) {
                # $sub is one of our wrappers around a CORE sub or a
                # user sub.  Instead of wrapping our wrapper, lets just
                # generate a new wrapper for the original sub.
                # - NB: the current wrapper might be for a different class
                #   than the one we are generating now (e.g. some limited
                #   mixing between use Fatal + use autodie can occur).
                # - Even for nested autodie, we need this as the leak guards
                #   differ.
                my $s = $Is_fatalised_sub{$sref};
                if (defined($s)) {
                    # It is a wrapper for a user sub
                    $sub = $s;
                } else {
                    # It is a wrapper for a CORE:: sub
                    $core = 1;
                    $call = "CORE::$name";
                    $proto = $CORE_prototype_cache{$call};
                }
            }

            # A regular user sub, or a user sub wrapping a
            # core sub.

            if (!$core) {
                # A non-CORE sub might have hints and such...
                $proto = prototype($sref);
                $call = '&amp;$sref';
                require autodie::hints;

                $hints = autodie::hints-&gt;get_hints_for( $sref );

                # If we've insisted on hints, but don't have them, then
                # bail out!

                if ($insist and not $hints) {
                    croak(sprintf(ERROR_NOHINTS, $name));
                }

                # Otherwise, use the default hints if we don't have
                # any.

                $hints ||= autodie::hints::DEFAULT_HINTS();
            }

        }

    } elsif ($sub eq $ini &amp;&amp; $sub !~ /^CORE::GLOBAL::/) {
        # Stray user subroutine
        croak(sprintf(ERROR_NOTSUB,$sub));

    } elsif ($name eq 'system') {

        # If we're fatalising system, then we need to load
        # helper code.

        # The business with $E is to avoid clobbering our caller's
        # $@, and to avoid $@ being localised when we croak.

        my $E;

        {
            local $@;

            eval {
                require IPC::System::Simple; # Only load it if we need it.
                require autodie::exception::system;
            };
            $E = $@;
        }

        if ($E) { croak ERROR_NO_IPC_SYS_SIMPLE; }

        # Make sure we're using a recent version of ISS that actually
        # support fatalised system.
        if ($IPC::System::Simple::VERSION &lt; MIN_IPC_SYS_SIMPLE_VER) {
            croak sprintf(
            ERROR_IPC_SYS_SIMPLE_OLD, MIN_IPC_SYS_SIMPLE_VER,
            $IPC::System::Simple::VERSION
            );
        }

        $call = 'CORE::system';
        $core = 1;

    } elsif ($name eq 'exec') {
        # Exec doesn't have a prototype.  We don't care.  This
        # breaks the exotic form with lexical scope, and gives
        # the regular form a "do or die" behavior as expected.

        $call = 'CORE::exec';
        $core = 1;

    } else {            # CORE subroutine
        $call = "CORE::$name";
        if (exists($CORE_prototype_cache{$call})) {
            $proto = $CORE_prototype_cache{$call};
        } else {
            my $E;
            {
                local $@;
                $proto = eval { prototype $call };
                $E = $@;
            }
            croak(sprintf(ERROR_NOT_BUILT,$name)) if $E;
            croak(sprintf(ERROR_CANT_OVERRIDE,$name)) if not defined $proto;
            $CORE_prototype_cache{$call} = $proto;
        }
        $core = 1;
    }

    # TODO: This caching works, but I don't like using $void and
    # $lexical as keys.  In particular, I suspect our code may end up
    # wrapping already wrapped code when autodie and Fatal are used
    # together.

    # NB: We must use '$sub' (the name plus package) and not
    # just '$name' (the short name) here.  Failing to do so
    # results code that's in the wrong package, and hence has
    # access to the wrong package filehandles.

    $cache = $Cached_fatalised_sub{$class}{$sub};
    if ($lexical) {
        $cache_type = CACHE_AUTODIE_LEAK_GUARD;
    } else {
        $cache_type = CACHE_FATAL_WRAPPER;
        $cache_type = CACHE_FATAL_VOID if $void;
    }

    if (my $subref = $cache-&gt;{$cache_type}) {
        $install_subs-&gt;{$name} = $subref;
        return $sref;
    }

    # If our subroutine is reusable (ie, not package depdendent),
    # then check to see if we've got a cached copy, and use that.
    # See RT #46984. (Thanks to Niels Thykier for being awesome!)

    if ($core &amp;&amp; exists $reusable_builtins{$call}) {
        # For non-lexical subs, we can just use this cache directly
        # - for lexical variants, we need a leak guard as well.
        $code = $reusable_builtins{$call}{$lexical};
        if (!$lexical &amp;&amp; defined($code)) {
            $install_subs-&gt;{$name} = $code;
            return $sref;
        }
    }

    if (!($lexical &amp;&amp; $core) &amp;&amp; !defined($code)) {
        # No code available, generate it now.
        my $wrapper_pkg = $pkg;
        $wrapper_pkg = undef if (exists($reusable_builtins{$call}));
        $code = $class-&gt;_compile_wrapper($wrapper_pkg, $core, $call, $name,
                                         $void, $lexical, $sub, $sref,
                                         $hints, $proto);
        if (!defined($wrapper_pkg)) {
            # cache it so we don't recompile this part again
            $reusable_builtins{$call}{$lexical} = $code;
        }
    }

    # Now we need to wrap our fatalised sub inside an itty bitty
    # closure, which can detect if we've leaked into another file.
    # Luckily, we only need to do this for lexical (autodie)
    # subs.  Fatal subs can leak all they want, it's considered
    # a "feature" (or at least backwards compatible).

    # TODO: Cache our leak guards!

    # TODO: This is pretty hairy code.  A lot more tests would
    # be really nice for this.

    my $installed_sub = $code;

    if ($lexical) {
        $installed_sub = $class-&gt;_make_leak_guard($filename, $code, $sref, $call,
                                                  $pkg, $proto);
    }

    $cache-&gt;{$cache_type} = $code;

    $install_subs-&gt;{$name} = $installed_sub;

    # Cache that we've now overridden this sub.  If we get called
    # again, we may need to find that find subroutine again (eg, for hints).

    $Is_fatalised_sub{$installed_sub} = $sref;

    return $sref;

}

# This subroutine exists primarily so that child classes can override
# it to point to their own exception class.  Doing this is significantly
# less complex than overriding throw()

sub exception_class { return "autodie::exception" };

{
    my %exception_class_for;
    my %class_loaded;

    sub throw {
        my ($class, @args) = @_;

        # Find our exception class if we need it.
        my $exception_class =
             $exception_class_for{$class} ||= $class-&gt;exception_class;

        if (not $class_loaded{$exception_class}) {
            if ($exception_class =~ /[^\w:']/) {
                confess "Bad exception class '$exception_class'.\nThe '$class-&gt;exception_class' method wants to use $exception_class\nfor exceptions, but it contains characters which are not word-characters or colons.";
            }

            # Alas, Perl does turn barewords into modules unless they're
            # actually barewords.  As such, we're left doing a string eval
            # to make sure we load our file correctly.

            my $E;

            {
                local $@;   # We can't clobber $@, it's wrong!
                my $pm_file = $exception_class . ".pm";
                $pm_file =~ s{ (?: :: | ' ) }{/}gx;
                eval { require $pm_file };
                $E = $@;    # Save $E despite ending our local.
            }

            # We need quotes around $@ to make sure it's stringified
            # while still in scope.  Without them, we run the risk of
            # $@ having been cleared by us exiting the local() block.

            confess "Failed to load '$exception_class'.\nThis may be a typo in the '$class-&gt;exception_class' method,\nor the '$exception_class' module may not exist.\n\n $E" if $E;

            $class_loaded{$exception_class}++;

        }

        return $exception_class-&gt;new(@args);
    }
}

# Creates and returns a leak guard (with prototype if needed).
sub _make_leak_guard {
    my ($class, $filename, $wrapped_sub, $orig_sub, $call, $pkg, $proto) = @_;

    # The leak guard is rather lengthly (in fact it makes up the most
    # of _make_leak_guard).  It is possible to split it into a large
    # "generic" part and a small wrapper with call-specific
    # information.  This was done in v2.19 and profiling suggested
    # that we ended up using a substantial amount of runtime in "goto"
    # between the leak guard(s) and the final sub.  Therefore, the two
    # parts were merged into one to reduce the runtime overhead.

    my $leak_guard = sub {
        my $caller_level = 0;
        my $caller;

        while ( ($caller = (caller $caller_level)[1]) =~ m{^\(eval \d+\)$} ) {

            # If our filename is actually an eval, and we
            # reach it, then go to our autodying code immediatately.

            last if ($caller eq $filename);
            $caller_level++;
        }

        # We're now out of the eval stack.

        if ($caller eq $filename) {
            # No leak, call the wrapper.  NB: In this case, it doesn't
            # matter if it is a CORE sub or not.
            if (!defined($wrapped_sub)) {
                # CORE sub that we were too lazy to compile when we
                # created this leak guard.
                die "$call is not CORE::&lt;something&gt;"
                    if substr($call, 0, 6) ne 'CORE::';

                my $name = substr($call, 6);
                my $sub = $name;
                my $lexical = 1;
                my $wrapper_pkg = $pkg;
                my $code;
                if (exists($reusable_builtins{$call})) {
                    $code = $reusable_builtins{$call}{$lexical};
                    $wrapper_pkg = undef;
                }
                if (!defined($code)) {
                    $code = $class-&gt;_compile_wrapper($wrapper_pkg,
                                                     1, # core
                                                     $call,
                                                     $name,
                                                     0, # void
                                                     $lexical,
                                                     $sub,
                                                     undef, # subref (not used for core)
                                                     undef, # hints (not used for core)
                                                     $proto);

                    if (!defined($wrapper_pkg)) {
                        # cache it so we don't recompile this part again
                        $reusable_builtins{$call}{$lexical} = $code;
                    }
                }
                # As $wrapped_sub is "closed over", updating its value will
                # be "remembered" for the next call.
                $wrapped_sub = $code;
            }
            goto $wrapped_sub;
        }

        # We leaked, time to call the original function.
        # - for non-core functions that will be $orig_sub
        # - for CORE functions, $orig_sub may be a trampoline
        goto $orig_sub if defined($orig_sub);

        # We are wrapping a CORE sub and we do not have a trampoline
        # yet.
        #
        # If we've cached a trampoline, then use it.  Usually only
        # resuable subs will have cache hits, but non-reusuably ones
        # can get it as well in (very) rare cases.  It is mostly in
        # cases where a package uses autodie multiple times and leaks
        # from multiple places.  Possibly something like:
        #
        #  package Pkg::With::LeakyCode;
        #  sub a {
        #      use autodie;
        #      code_that_leaks();
        #  }
        #
        #  sub b {
        #      use autodie;
        #      more_leaky_code();
        #  }
        #
        # Note that we use "Fatal" as package name for reusable subs
        # because A) that allows us to trivially re-use the
        # trampolines as well and B) because the reusable sub is
        # compiled into "package Fatal" as well.

        $pkg = 'Fatal' if exists $reusable_builtins{$call};
        $orig_sub = $Trampoline_cache{$pkg}{$call};

        if (not $orig_sub) {
            # If we don't have a trampoline, we need to build it.
            #
            # We only generate trampolines when we need them, and
            # we can cache them by subroutine + package.
            #
            # As $orig_sub is "closed over", updating its value will
            # be "remembered" for the next call.

            $orig_sub = make_core_trampoline($call, $pkg, $proto);

            # We still cache it despite remembering it in $orig_sub as
            # well.  In particularly, we rely on this to avoid
            # re-compiling the reusable trampolines.
            $Trampoline_cache{$pkg}{$call} = $orig_sub;
        }

        # Bounce to our trampoline, which takes us to our core sub.
        goto $orig_sub;
    };  # &lt;-- end of leak guard

    # If there is a prototype on the original sub, copy it to the leak
    # guard.
    if (defined $proto) {
        # The "\&amp;" may appear to be redundant but set_prototype
        # croaks when it is removed.
        set_prototype(\&amp;$leak_guard, $proto);
    }

    return $leak_guard;
}

sub _compile_wrapper {
    my ($class, $wrapper_pkg, $core, $call, $name, $void, $lexical, $sub, $sref, $hints, $proto) = @_;
    my $real_proto = '';
    my @protos;
    my $code;
    if (defined $proto) {
        $real_proto = " ($proto)";
    } else {
        $proto = '@';
    }

    @protos = fill_protos($proto);
    $code = qq[
        sub$real_proto {
    ];

    if (!$lexical) {
        $code .= q[
           local($", $!) = (', ', 0);
        ];
    }

    # Don't have perl whine if exec fails, since we'll be handling
    # the exception now.
    $code .= "no warnings qw(exec);\n" if $call eq "CORE::exec";

    $code .= $class-&gt;_write_invocation($core, $call, $name, $void, $lexical,
                                       $sub, $sref, @protos);
    $code .= "}\n";
    warn $code if $Debug;

    # I thought that changing package was a monumental waste of
    # time for CORE subs, since they'll always be the same.  However
    # that's not the case, since they may refer to package-based
    # filehandles (eg, with open).
    #
    # The %reusable_builtins hash defines ones we can aggressively
    # cache as they never depend upon package-based symbols.

    my $E;

    {
        no strict 'refs'; ## no critic # to avoid: Can't use string (...) as a symbol ref ...
        local $@;
        if (defined($wrapper_pkg)) {
            $code = eval("package $wrapper_pkg; require Carp; $code");  ## no critic
        } else {
            $code = eval("require Carp; $code");  ## no critic

        }
        $E = $@;
    }

    if (not $code) {
        my $true_name = $core ? $call : $sub;
        croak("Internal error in autodie/Fatal processing $true_name: $E");
    }
    return $code;
}

# For some reason, dying while replacing our subs doesn't
# kill our calling program.  It simply stops the loading of
# autodie and keeps going with everything else.  The _autocroak
# sub allows us to die with a vengeance.  It should *only* ever be
# used for serious internal errors, since the results of it can't
# be captured.

sub _autocroak {
    warn Carp::longmess(@_);
    exit(255);  # Ugh!
}

1;

__END__

=head1 NAME

Fatal - Replace functions with equivalents which succeed or die

=head1 SYNOPSIS

    use Fatal qw(open close);

    open(my $fh, "&lt;", $filename);  # No need to check errors!

    use File::Copy qw(move);
    use Fatal qw(move);

    move($file1, $file2); # No need to check errors!

    sub juggle { . . . }
    Fatal-&gt;import('juggle');

=head1 BEST PRACTICE

B&lt;Fatal has been obsoleted by the new L&lt;autodie&gt; pragma.&gt; Please use
L&lt;autodie&gt; in preference to C&lt;Fatal&gt;.  L&lt;autodie&gt; supports lexical scoping,
throws real exception objects, and provides much nicer error messages.

The use of C&lt;:void&gt; with Fatal is discouraged.

=head1 DESCRIPTION

C&lt;Fatal&gt; provides a way to conveniently replace
functions which normally return a false value when they fail with
equivalents which raise exceptions if they are not successful.  This
lets you use these functions without having to test their return
values explicitly on each call.  Exceptions can be caught using
C&lt;eval{}&gt;.  See L&lt;perlfunc&gt; and L&lt;perlvar&gt; for details.

The do-or-die equivalents are set up simply by calling Fatal's
C&lt;import&gt; routine, passing it the names of the functions to be
replaced.  You may wrap both user-defined functions and overridable
CORE operators (except C&lt;exec&gt;, C&lt;system&gt;, C&lt;print&gt;, or any other
built-in that cannot be expressed via prototypes) in this way.

If the symbol C&lt;:void&gt; appears in the import list, then functions
named later in that import list raise an exception only when
these are called in void context--that is, when their return
values are ignored.  For example

    use Fatal qw/:void open close/;

    # properly checked, so no exception raised on error
    if (not open(my $fh, '&lt;', '/bogotic') {
        warn "Can't open /bogotic: $!";
    }

    # not checked, so error raises an exception
    close FH;

The use of C&lt;:void&gt; is discouraged, as it can result in exceptions
not being thrown if you I&lt;accidentally&gt; call a method without
void context.  Use L&lt;autodie&gt; instead if you need to be able to
disable autodying/Fatal behaviour for a small block of code.

=head1 DIAGNOSTICS

=over 4

=item Bad subroutine name for Fatal: %s

You've called C&lt;Fatal&gt; with an argument that doesn't look like
a subroutine name, nor a switch that this version of Fatal
understands.

=item %s is not a Perl subroutine

You've asked C&lt;Fatal&gt; to try and replace a subroutine which does not
exist, or has not yet been defined.

=item %s is neither a builtin, nor a Perl subroutine

You've asked C&lt;Fatal&gt; to replace a subroutine, but it's not a Perl
built-in, and C&lt;Fatal&gt; couldn't find it as a regular subroutine.
It either doesn't exist or has not yet been defined.

=item Cannot make the non-overridable %s fatal

You've tried to use C&lt;Fatal&gt; on a Perl built-in that can't be
overridden, such as C&lt;print&gt; or C&lt;system&gt;, which means that
C&lt;Fatal&gt; can't help you, although some other modules might.
See the L&lt;/"SEE ALSO"&gt; section of this documentation.

=item Internal error: %s

You've found a bug in C&lt;Fatal&gt;.  Please report it using
the C&lt;perlbug&gt; command.

=back

=head1 BUGS

C&lt;Fatal&gt; clobbers the context in which a function is called and always
makes it a scalar context, except when the C&lt;:void&gt; tag is used.
This problem does not exist in L&lt;autodie&gt;.

"Used only once" warnings can be generated when C&lt;autodie&gt; or C&lt;Fatal&gt;
is used with package filehandles (eg, C&lt;FILE&gt;).  It's strongly recommended
you use scalar filehandles instead.

=head1 AUTHOR

Original module by Lionel Cons (CERN).

Prototype updates by Ilya Zakharevich &lt;ilya@math.ohio-state.edu&gt;.

L&lt;autodie&gt; support, bugfixes, extended diagnostics, C&lt;system&gt;
support, and major overhauling by Paul Fenwick &lt;pjf@perltraining.com.au&gt;

=head1 LICENSE

This module is free software, you may distribute it under the
same terms as Perl itself.

=head1 SEE ALSO

L&lt;autodie&gt; for a nicer way to use lexical Fatal.

L&lt;IPC::System::Simple&gt; for a similar idea for calls to C&lt;system()&gt;
and backticks.

=for Pod::Coverage exception_class fill_protos one_invocation throw write_invocation ERROR_NO_IPC_SYS_SIMPLE LEXICAL_TAG

=cut
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